This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/AU98/00686 which has an International filing date of Aug. 26, 1998, which designated the United States of America.
This invention relates to an improved arrangement for seats, such as motor vehicle seats, which have a backrest frame that is adjustable relative to a seat base via a seat recliner system.
In seats of the above-indicated types, especially with those for automotive use, there has been a considerable effort in recent years to introduce weight-reducing improvements. One such improvement has seen the introduction of seat backrest frames cast from light alloys or molded from engineering plastics. These backrest frames are connected to the seat base via the seat recliner system. Accordingly, in order to achieve a connection which does not adversely impair the overall strength of the seat, it has been necessary to adopt a seat back connection of a form which substantially offsets the weight-reduction achieved by the backrest frame.
One form of connection for cast or molded backrest frames has utilized steel reinforcement beams, each of which extends up a respective side of the backrest frame. Another form utilizes a much heavier recliner system with bolting or riveting of vertical arms which similarly extend up the backrest frame to enable multiple fixings. In each case, the overall weight saving is less than achieved in the backrest frame, while there also are disadvantages in costs, materials usage and assembly time. Also, the connections can utilize space which otherwise would be available for other mechanisms, such as inflatable air-cushions and at least part of an operating mechanism for an adjustable lumbar support.
According to the present invention there is provided a seat arrangement including a backrest frame and a base frame. The backrest frame is connectable, adjacent the lower extent of each of opposite sides thereof, to respective mounting means that facilitate pivotable mounting of the backrest frame to the base frame. Each of the mounting means includes a respective load dispersing member, and the backrest frame is connected to the mounting means by fasteners inserted laterally to the frame, through the frame and the load dispersing member of the mounting means, the fasteners on fastening, drawing each load dispersing member into a respective recess defined by the backrest frame. Each recess has a complimentary form with the load dispersing member to define respective base surfaces through which the fasteners extend, and opposes side surfaces. The fasteners, upon fastening the backrest frame to the mounting means, causes each of the load dispersing members to clamp into the respective recess, whereby respective adjacent side surfaces of the recess and the load dispersing member are urged into a surface to surface contact.
The side surface of each load dispersing member and each of the recesses may be substantially parallel, although they preferably diverge.
In a preferred arrangement, each mounting means includes a mounting member, separately formed from the load dispersing member. The fasteners extend through the frame and the member and through the load dispersing member. In an alternative arrangement, the mounting member and the load dispersing member are formed as a single component, either integrally or by suitable connecting means, such that the fasteners extend through the frame and the load dispersing member.
The fasteners may comprise threaded screws or bolts. Alternatively, they may comprise rivets.
There preferably are two fasteners, with these most preferably spaced from each other in the front to rear direction relative to the backrest frame when the latter is in a normal in-use orientation. However, the fasteners can be spaced in other directions, for example, such as upwardly spaced.
Each load dispersing member preferably is formed of steel. In that case, it can be pressed or stamped from steel plate to provide a central region between two opposed diverging wing portions. The load dispersing member may be open between adjacent ends of the respective opposed wing portions, or it may be closed. In latter arrangement, the load dispersing member is somewhat cup- shaped. The central region may have holes formed therein for receiving the fasteners. In the case of threaded fasteners, the holes may be threaded. Alternatively, threaded nuts can be provided, with the nuts preferably welded to the central region. Alternatively, the central region can have burst holes for use with self-threading fasteners.
Rather than being formed from steel plate, each load dispersing member can be cast from a suitable metal such as a light alloy, preferably a high strength alloy, which might undergo suitable strengthening treatment during formation, such as heat treatment. The load dispersing member might additionally, or alternatively, be coated with a suitable strengthening coating. In these cases, the load dispersing member again may have a central region between two wing portions, with the wing portions preferably diverging. However, strengthening ribs preferably are provided between the wing portions. Alternatively, the load dispersing member may be of solid form, defining a central surface between two diverging side surfaces.
The recess defined by the backrest frame, at each of the opposite sides thereof, opens laterally. Also, each recess is defined by a wall portion of the frame which provides two side surfaces, preferably two mutually inclined diverging side surfaces, separated by a base surface through which the fasteners extend. The recess may be open at one or each end thereof, i.e., between the side surfaces. Alternatively, it may be closed at each end so as to enclose the load dispersing member around the periphery of the latter.
In one convenient arrangement, the load dispersing member is pressed from steel plate to provide a central region between two similarly diverging wing portions. In that arrangement, an included angle between each wing portion, and the central region is slightly in excess of a corresponding included angle between each side surface and the base surface of the respective recess. The arrangement is such that, as fasteners are applied to draw the load dispersing member into the recess to achieve surface to surface contact, the wing portions are caused to flex so that each is substantially parallel to a side surface of the recess. It is preferable that the wing portions are caused to flex only slightly, so that the level of strain induced in the load dispersing member when drawn into the recess is relatively low. The flex principally has the effect of reducing or eliminating free play between the load dispersing member and the backrest frame, so as to prevent movement therebetween under load, and to provide surface to surface contact between the side surfaces of the recess and the diverging wings of the load dispersing member for acceptable load transfer.